#include <cstring> // strcpy, strcat, strlen
#include <stdexcept> // std::bad_alloc
#include <iostream> // std::ostream

class Integer{
  public:
    int value;

    Integer& operator+=(int a){
      value = a * 10 + value;
      return *this;
    }

    // 输出字符串内容
    friend std::ostream &operator<<(std::ostream &os, const Integer& vv) {
        return os << vv.value; // 使用 c_str() 返回 const char*
    }
};


int main() {
     Integer vv;
     vv.value = 1;
     std::cout << vv<< std::endl;
     vv += 10;
    std::cout << vv << std::endl;
}